This invention relates to a device and a method for bleeding compressor air in an engine.
It is known to extract compressor air from a compressor of an engine, in order to vary the mass flow through the compressor and to optimize the latter in respect of its aerodynamic stability. The bleeding of compressor air is used, for example, to prevent unstable operating states of a low-pressure compressor.
A device is known from U.S. Pat. No. 7,594,403 B2 for extracting compressor air from a low-pressure compressor, where in the wall of the low-pressure compressor openings are provided which can be released or closed by an adjusting ring arranged on the outside. The extracted compressor air is supplied to a secondary flow duct via bypass ducts. A device of this type for controllable bleeding of compressor air from a low-pressure compressor is also referred to as a booster bleed valve (BBV) system.
A turbofan engine is known from US 2002/0148216 A1 in which openings are provided behind a low-pressure compressor in the wall of the primary flow duct, via which openings compressor air is passed into an annular cavity. From this cavity, a plurality of ducts leads to a secondary flow duct of the engine. Each of these ducts is assigned a valve to open or close the respective duct.
In known BBV systems, only the positions “open” and “closed” are possible, for example by valve rings or valve flaps, since in the transitional positions the air is too heavily swirled. This has the disadvantage that it is not possible to make a defined setting of the airflow that is passed through the bypass duct, because with only partial release of the openings a high degree of swirling occurs in known BBV systems, leading to a loss of efficiency and an increase in noise.